Related Experiment Videos
Ultrastructural and functional analyses of nephropathy in calmodulin-induced diabetic transgenic mice
E C Carlson1, J L Audette, L M Klevay
1Department of Anatomy, University of North Dakota School of Medicine, Grand Forks, North Dakota 58202, USA.
Background:
Previous animal models of diabetic nephropathy have used diabetic animals for which the underlying defect was either uncertain or the diabetes was induced by potentially specific toxins. In this report, we describe the renal abnormalities in a transgenic mouse model that develops early-onset diabetes due to overexpression of calmodulin in pancreatic beta cells.
Methods:
Renal tissues were collected from normal and transgenic mice at 112, 182, and 300 days. These were prepared for light microscopic observation, stained with polyethylenimine (for anionic sites), or rendered acellular by detergent extraction prior to observation by transmission and scanning electron microscopy. Morphometric analysis of glomerular basement membrane thickness was carried out by the "orthogonal intercept" method. Twelve-hour urine samples of fed and fasting mice were collected for urine volume and glucose and protein analyses. Blood glucose, blood urea nitrogen, serum insulin, and creatinine were determined in 60-90-day-old and 255-day-old mice by established methods.
Results:
Morphometric analyses revealed age-related and transgene-related increases in glomerular basement membrane thickness. A 22% increase in transgenic diabetics over controls was seen at 112 days of age that developed to increases of 43% and 37% at 182 and 300 days of age, respectively. Mesangial matrix area was also increased markedly in transgenic mice. Surprisingly, even in the oldest diabetic mice, there was no reduction in anionic sites. Moreover, despite an eightfold increase in urine volume, these mice did not become significantly proteinuric.
Conclusions:
These results indicate that proteinuria of diabetes may be delayed or prevented by maintenance of a normal complement of glomerular basement membrane anionic sites. They also demonstrate that transgenic mice can provide a valuable model for discriminating between different aspects of diabetic nephropathy.
Insights
This study introduces a new transgenic mouse model for diabetic nephropathy. These mice show delayed proteinuria, suggesting preserved glomerular anionic sites protect against kidney damage in diabetes.
Area of Science:
- Nephrology
- Endocrinology
- Genetics
Background:
- Established animal models for diabetic nephropathy have limitations due to uncertain diabetic defects or toxin-induced diabetes.
- This study introduces a novel transgenic mouse model with early-onset diabetes caused by calmodulin overexpression in pancreatic beta cells.
Purpose of the Study:
- To characterize renal abnormalities in a transgenic mouse model of diabetes.
- To investigate the role of glomerular basement membrane anionic sites in the development of diabetic nephropathy.
Main Methods:
- Collected renal tissues from normal and transgenic mice at multiple time points (112, 182, 300 days).
- Utilized light microscopy, polyethylenimine staining for anionic sites, and electron microscopy (transmission and scanning).
- Performed morphometric analysis of glomerular basement membrane thickness and mesangial matrix area; analyzed urine and blood parameters.
Main Results:
- Demonstrated age-related and transgene-related increases in glomerular basement membrane thickness and mesangial matrix area in transgenic mice.
- Observed no reduction in glomerular anionic sites even in oldest diabetic mice.
- Noted a significant increase in urine volume but no significant proteinuria in transgenic mice.
Conclusions:
- Maintenance of glomerular basement membrane anionic sites may delay or prevent proteinuria in diabetes.
- Transgenic mice offer a valuable model for dissecting various aspects of diabetic nephropathy.